1. Field of the Invention
The present invention relates to the technical field of rare earth element (REE) production. More particularly, the present invention relates to rare earth constituents from phosphor, such as waste phosphor powders.
2. Description of Related Art
The conventional process for the production of rare earth elements (REEs) is through a mining process, wherein the mineral ore is processed through multiple steps to produce the REE. This is an expensive and time-consuming process due to the presence of several REEs in the ore, some of which may be in very low concentrations, thereby requiring additional concentration steps. Also, most mineral ores for REE have radioactive elements, such as Uranium and/or Thorium, which require very careful handling. Further, this process is environmentally taxing due to the generation of large amounts of waste by-products, some of which are toxic.
Rare earth containing phosphor powders are used in a variety of products such as fluorescent lamps, cathode ray tube (CRT) displays, plasma displays and light emitting diodes (LED). The most commonly used REE found in these phosphors are Lanthanum (La), Cerium (Ce), Europium (Eu), Terbium (Tb) and Yttrium (Y). In addition to the REE, these powders may contain Calcium (Ca), Barium (Ba), Strontium (Sr), Aluminum (Al), Mercury (Hg), Lead (Pb), Zinc (Zn), etc., in the elemental form or as oxides or phosphates. The REE Gadolinium (Gd) may also be found in some phosphors, particularly those derived at least in part from compact fluorescent bulb waste. When these products reach end-of-life, they are classified as electronic waste (e-waste) and sent to designated recycling centers. While the other parts of the products may be recovered, the waste phosphor powders have typically been sent to a landfill with no effort made to reclaim the rare earths from the waste material.